U.S. Pat. No. 5,589,563 (Robert S. Ward and Kathleen A. White) describes the use of surface modifying endgroups (SMEs) to tailor polymer surface properties. The '563 patent is entitled “SURFACE-MODIFYING ENDGROUPS FOR BIOMEDICAL POLYMERS”. The entire contents of U.S. Pat. No. 5,589,563 are hereby expressly incorporated by reference. As documented in the '563 patent, a variety of hydrophobic and hydrophilic endgroups has been demonstrated to enable the achievement of useful changes in surface properties of polymers. Such surface properties include biostability, protein adsorption, abrasion resistance, bacterial adhesion and proliferation, fibroblast adhesion, and coefficient of friction. SME polymers have also been used in low bulk concentration as surface modifying additives (SMAs) to SME-free base polymers.
As explained in U.S. Pat. No. 5,589,563, the surface activity of SMEs is high, in part because of the added mobility of polymer endgroups relative to backbone groups. An endgroup is tethered to the bulk polymer at only one point and is otherwise free to migrate to interfaces. This migration occurs spontaneously if the result is a reduction in system interfacial energy. Thus, hydrophobic groups such as silicone will migrate to air interfaces and hydrophilic groups such as poly(ethylene oxide) will migrate to aqueous interfaces. The surfaces of polymers containing SME endgroups will restructure following a change in their environment.
U.S. Pat. No. 5,589,563 teaches in lines 19-27 of column 8 that, where mixed endgroups are present in a single polymer, complex surface activity may be achieved. Of the specific polymers disclosed in the '563 patent, only those of Examples 6 and 8 may be considered to contain surface-modifying amphipathic moieties, as that terminology is used in the present invention.